@GL4M0URG1RL dispatch.meta is found in update\update.rpf\common\data. So, if you're using openiv, as you should, you should put modified dispatch.meta in mods\update\update.rpf\common\data.

As for the streets with no cars at all, I experienced that same problem not long ago myself. As you've done, I used the addoncars+racing variant. The result: a world with practically no cars in it. I think that variant is for people using other mods that add cars to the game. Not my case. What I did to get everything back to normal was to use the variant vanilla + race instead.